Laser beam scanning radiating apparatus

Abstract

A laser beam source radiates out laser beams such that they may intersect one another with predetermined angular spectra on a predetermined virtual plane. A Fourier transform lens array optical system, which is located in the vicinity of the virtual plane, divides the laser beams having impinged upon the virtual plane into small regions and carries out Fourier transform of the small regions. Phase modulators modulate the phases of the laser beams divided into the small regions such that the wave fronts of the laser beams after being subjected to the Fourier transform may have the same phase with respect to a predetermined direction as a whole. A scanning drive device drives the phase modulators such that the directions of travel of the laser beams radiated out of the Fourier transform lens array optical system may be changed. A first resonator mirror is located at a position that receives the scanned laser beams. A second resonator mirror is located at a position rearward from the laser beam source.

What is claimed is: 
     
       1. A laser beam scanning radiating apparatus comprising: i) a laser beam source which emits a plurality of laser beams at a wavelength such that the laser beams intersect one another with predetermined angular spectra on a predetermined virtual plane through which the laser beams pass;   ii) a transform optical system including a beam expander array dividing the laser beams having impinged upon the virtual plane into small regions and a Fourier transform lens array which carries out Fourier transforms of the small regions, said transform optical system being located in the vicinity of the virtual plane such that a front Fourier transform plane of said transform optical system substantially coincides with the virtual plane;   iii) phase modulating means for modulating each of the phases of the laser beams having been divided into the small regions by said beam expander array, said phase modulating means being positioned between said beam expander array and said Fourier transform lens array such that wave fronts of the plurality of the laser beams subjected to the Fourier transform by said Fourier transform lens array in said transform optical system are continuously smoothly connected with one another;   iv) scanning drive means for driving said phase modulating means in order to change directions of travel of the laser beams emitted from said transform optical system; and   v) a laser resonator mirror optical system including, a) a first laser resonator mirror, which receives the laser beams having been scanned by said scanning drive means, and which reflects said laser beams having been scanned back towards said transform optical system, and   b) a second laser resonator mirror, which is located at a position rearward from said laser beam source,     wherein a plurality of Fourier transformed patterns of the laser beams are reproduced on the Fourier transform plane of said transform optical system at equal intervals and with a same phase with respect to a predetermined direction.   
     
     
       2. An apparatus as defined in claim 1, wherein a product of the array pitch of said transform optical system and a variation of an angular spectrum of each of the laser beams at the respective positions at which the laser beams intersect one another, is within the range of larger than 0 to smaller than 2, such that an intensity distribution pattern of the combined laser beam, which occurs from optical coupling of the plurality of the laser beams by said transform optical system, said phase modulating means and said laser resonator mirror optical system, becomes substantially single-lobed. 
     
     
       3. An apparatus as defined in claim 2 further comprising a Fourier transform lens located between the back end face of said laser beam source and said second laser resonator mirror such that a Fourier transform plane of said Fourier transform lens coincides with the back end face of said laser beam source, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said Fourier transform lens and said second laser resonator mirror as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       4. An apparatus as defined in claim 2, further comprising a collimator lens array and a prism located between the back end face of said laser beam source and said second laser resonator mirror, said second laser resonator mirror being located on reflecting surfaces of said prism, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said collimator lens array and said prism as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       5. An apparatus as defined in claim 2, wherein said second laser resonator mirror includes a phase-conjugate mirror and a converging optical system located between the back end face of said laser beam source and said phase-conjugate mirror, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said converging optical system and said phase-conjugate mirror as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       6. An apparatus as defined in claim 1, wherein said laser beam source is an array laser beam source including an array of a plurality of laser beam sources, which respectively emit the laser beams. 
     
     
       7. An apparatus as defined in claim 6, further comprising a Fourier transform lens located between the back end face of said laser beam source and said second laser resonator mirror such that a Fourier transform plane of said Fourier transform lens coincides with the back end face of said laser beam source, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said Fourier transform lens and said second laser resonator mirror as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       8. An apparatus as defined in claim 6, further comprising a collimator lens array and a prism located between the back end face of said laser beam source and said second laser resonator mirror, said second laser resonator mirror being located on reflecting surfaces of said prism, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said collimator lens array and said prism as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       9. An apparatus as defined in claim 6, wherein said second laser resonator mirror includes a phase-conjugate mirror and a converging optical system located between the back end face of said laser beam source and said phase-conjugate mirror, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said converging optical system and said phase-conjugate mirror as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       10. An apparatus as defined in claim 6, wherein said laser beam source includes a plurality of laser beam sources arranged in a skew lattice pattern in a plane normal to the optical axis, said laser beam source emitting the plurality of the laser beams from positions located in the skew lattice pattern, and said Fourier transform lens array and said beam expander array of said transform optical system, and phase modulating elements of said phase modulating means are arrayed in a lattice pattern reciprocal with the skew lattice pattern of the laser beam emitting positions.   
     
     
       11. An apparatus as defined in claim 1, wherein said laser beam source is a bulk-like laser beam source capable of emitting the laser beams from arbitrary positions lying in a plane, which is parallel to said predetermined virtual plane. 
     
     
       12. An apparatus as defined in claim 11, further comprising a Fourier transform lens is located between the back end face of said laser beam source and said second laser resonator mirror such that a Fourier transform plane of said Fourier transform lens coincides with the back end face of said laser beam source, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said Fourier transform lens and said second laser resonator mirror as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       13. An apparatus as defined in claim 11, further comprising a collimator lens array and a prism located between the back end face of said laser beam source and said second laser resonator mirror, said second laser resonator mirror being located on reflecting surfaces of said prism, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said collimator lens array and said prism as a phase-conjugate laser beam, and is thereafter emitted from a front end of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       14. An apparatus as defined in claim 11, wherein said second laser resonator mirror includes a phase-conjugate mirror and a converging optical system located between the back end face of said laser beam source and said phase-conjugate mirror, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said converging optical system and said phase-conjugate mirror as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       15. An apparatus as defined in claim 11, wherein said laser beam source includes a plurality of laser beam sources arranged in a skew lattice pattern in a plane normal to the optical axis, said laser beam source emitting the plurality of the laser beams from positions located in the skew lattice pattern, and said Fourier transform lens array and said beam expander array of said transform optical system, and phase modulating elements of said phase modulating means are arrayed in a lattice pattern reciprocal with the skew lattice pattern of the laser beam emitting positions.   
     
     
       16. An apparatus as defined in claim 1, further comprising a Fourier transform lens located between the back end face of said laser beam source and said second laser resonator mirror such that a Fourier transform plane of said Fourier transform lens coincides with the back end face of said laser beam source, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said Fourier transform lens and said second laser resonator mirror as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       17. An apparatus as defined in claim 1, further comprising a collimator lens array and a prism located between the back end face of said laser beam source and said second laser resonator mirror, said second laser resonator mirror being located on reflecting surfaces of said prism, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said collimator lens array and said prism as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       18. An apparatus as defined in claim 1, wherein said second laser resonator mirror includes a phase-conjugate mirror and a converging optical system located between the back end face of said laser beam source and said phase-conjugate mirror, wherein each of the laser beams reflected by said first laser resonator mirror, entered into said laser beam source, and emitted from the back end face of said laser beam source, is reflected and again enters the back end face of said laser beam source via said converging optical system and said phase-conjugate mirror as a phase-conjugate laser beam, and is thereafter emitted from a front end face of said laser beam source as a laser beam which is a phase-conjugate of the laser beam reflected by said first laser resonator mirror and emitted from the back end face of said laser beam source.   
     
     
       19. An apparatus as defined in claim 1, wherein said laser beam source includes a plurality of laser beam sources arranged in a skew lattice pattern in a plane normal to the optical axis, said laser beam source emitting the plurality of the laser beams from positions located in the skew lattice pattern, and said Fourier transform lens array and said beam expander array of said transform optical system, and phase modulating elements of said phase modulating means are arrayed in a lattice pattern reciprocal with the skew lattice pattern of the laser beam emitting positions.   
     
     
       20. An apparatus as defined in claim 1, wherein the plurality of Fourier transformed patterns of the laser beams are reproduced on the Fourier transform plane of said transform optical system at equal intervals and with a same phase with respect to a predetermined direction by appropriate selection of each of the following parameters: a focal length of said transform optical system, an array pitch of said transform optical system, a number of the plurality of the laser beams emitted by said laser beam source, the wavelength of the laser beam source, and the variation of the angular spectrum of each of the laser beams at the respective positions at which the laser beams intersect one another. 
     
     
       21. An apparatus as defined in claim 20, wherein said plurality of Fourier transformed patterns are reproduced at equal intervals and with a same phase with respect to a predetermined direction by providing elements of the apparatus which satisfy the following equations:   I=pΔα       p=λΔαf.sub.2 N     where I is an integer other than 0, p is the lens pitch of the transform optical system, λ is the wavelength of the laser beam source, Δα is the variation in angular spectrum, f 2  is the focal length of the transform optical system and N is the number of the laser beams.   
     
     
       22. An apparatus as defined in claim 21, wherein said apparatus further comprises a Fourier transform lens situated between said laser beam source and said transform optical system, and wherein said laser beam source is an array laser, and wherein said variation in angular spectrum is defined as ##EQU31## where f 1  is a focal length of said Fourier transform lens, and d 1  is an array pitch of said array laser. 
     
     
       23. An apparatus as defined in claim 1, wherein said first laser resonator mirror is a planar mirror. 
     
     
       24. A method of scanning a laser beam at equal intervals and with a same phase with respect to a predetermined direction comprising the steps of: emitting a plurality of laser beams at a wavelength;   intersecting the laser beams with one another with predetermined angular spectra on a predetermined virtual plane through which the laser beams pass;   dividing the laser beams having impinged upon the virtual plane into small regions using a beam expander array;   Fourier transforming the small regions using a Fourier transform lens array;   locating a transform optical system including the beam expander array and the transform lens array in the vicinity of the virtual plane such that a front Fourier transform plane of said transform optical system substantially coincides with the virtual plane;   modulating each of the phases of the laser beams having been divided into the small regions such that wave fronts of the plurality of the laser beams subjected said Fourier transforming step are continuously smoothly connected with one another;   driving said modulating means step in order to change directions of travel of the laser beams emitted from the transform optical system;   reflecting, after said driving step, the laser beams back towards the transform optical system;   positioning a laser resonator mirror rearward from said laser beam source; and   reproducing a plurality of Fourier transformed patterns of the laser beams at equal intervals and with a same phase with respect to a predetermined direction of the Fourier transform plane of said transform optical system by selecting appropriate values for the following parameters: a focal length of the transform optical system, an array pitch of the transform optical system, a number of the plurality of the laser beams, a wavelength of the laser beams, and the variation of the angular spectrum of each of the laser beams at the respective positions at which the laser beams intersect one another.